Sorry, I haven't been on in a while. Actually, the problem lie with insufficient solder on the input jack. A nice little dab of solder, and Voila no more hum. Thanks for the input, I will be sure to backtrack thru the other posts and keep you guys in mind if I need to repair any other amp I may have lying around. Again, thanks, you guys rock!

I have a Peavey Blazer 158 that I got from my brother. It worked fine for a while, but one day I got a loud hum whenever I plug my guitar cord into it. The hum does not seem to be present with no guitar plugged in, just when I try to plug in a guitar. Any ideas on where I might start to try and fix this?